How to Cut Glass

Whether setting a window pane, creating a stained glass mosaic, or doing some other project, cutting glass is a handy skill that isn't difficult to pick up. With the right tools and a steady hand, anyone can start cutting standard glass at home.

Steps

Part One of Four:Preparation

1

Set up your work area. You'll need a large flat surface, preferably one that is slightly soft and won't scratch your glass. Work in an area that is easy to clean.

Avoid working over carpet because of the risk of getting glass shards on the floor if the glass breaks.

For their own safety keep pets and children away from your workspace and materials.

2

Clean the glass surface in the area where you plan to make cuts. Any grime or silica on the glass can ruin your score. Wipe these away by running a cloth or your finger along the surface of the glass where you plan to score.

3

Obtain a glass cutter and some light oil. Glass cutters are about the size of a pencil and use a diamond or a hardened wheel to mark a score into glass so that it can be broken cleanly along a line. You can buy cutting oil at a stained glass store or use a small amount of kerosene.

4

Measure and mark where you want to score. The score must run from one edge of the glass to the other edge. You can write on the glass with a marker (preferably with a straight edge, if you are cutting a straight line. You can also mark on paper and place the glass on top of the paper.

Cut should not be very long. Scores longer than two feet have a high failure rate when breaking.

Make sure your marks leave about six inches of glass on each side to grip and break. If you cut smaller pieces, you may need to use special tools, like pliers or a light hammer, to break off glass you can't get a hold of.

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Part Two of Four:Scoring the Glass

1

Dip the cutter in the oil and grasp it like a pencil. An oiled cutter creates a smoother score line. Make sure to look at the wheel and make sure it is lined up the way you want the glass to cut.

2

Lay out a straight edge. Use a yardstick or a normal desk ruler. You need something that has a thick enough profile that it won't conflict with the wheel on the cutter.

3

Apply pressure to the glass and you pull the cutter along the surface, rolling on the small carbide wheel. Listen for a smooth sound like ripping silk. A gritty sound means that you are pushing too hard or that you did not oil your cutter. The less sound you make, the better your score will be.

If you push too hard (a very common mistake), your cut gets "hot," meaning that it snaps and pops.

You are aiming to get a uniform score. If you are pressing too hard in one spot and perfectly in another, the glass will not break the way that you want it to. Microscopic imperfections in your score will cause your cut to go askew.

4

Run the cutter smoothly from one edge to the other. Do not run back and forth over the line if you miss a spot.

5

Check your score. You want a score that is not popping and is barely visible, if you were to wipe the oil away. It should look like a small scratch, nothing more. Make sure it runs completely from one edge to the other.

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Part Three of Four:Breaking and Smoothing

1

Grasp each side of the cut carefully in your hands. Hold the glass as if you were trying to break a potato chip in half with two hands.

2

Apply minor pressure from the wrist to break the glass along your score. Your elbows do not move. Simply twist your wrists (your right wrist will turn clockwise and your left will turn counterclockwise). Imagine that the score you made is half the depth of the glass and now you need to "open it up" by using the score as a weak spot. You're done as soon as you have two pieces of glass instead of the one you started with.

When the glass breaks, it may simply start as a "run." If it only runs an inch or so, apply a little more twisting pressure and it will continue to run.

3

Use fine sandpaper or a sharpening stone to remove the sharp edge. This edge will be where the vertical edge meets the horizontal surfaces. Not only does sanding reduce the chances of your being cut, but sanded glass is less likely to chip along the edges and has some added strength.

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Part Four of Four:Cutting on a Curve

1

Follow a pattern that connects to the edge. If you are cutting a freehand shape, make sure you are breaking along lines that run from edge to edge. Mark your lines with a marker or set your glass over your pattern.

2

Use several straight lines to cut a sharp curve. You should be able to score along gentle curves normally with a steady hand. For tighter curves, make a series of marks that run along part of the curve and skew off at a tangent outside the piece you want.

3

Flip the glass over and gently press on the center of your score from the backside. You will start a run this way. Follow the run with light pressure and you can watch the glass separate where you scored it. If your score is too close to the edge of a piece of glass, it may run to the edge instead of along your score because that is the easiest path for the run to take.

4

Make some relief cuts to remove small pieces at a time instead of all at once. The smaller the relief cuts, the more accurate your cut will be. Grip smaller pieces with pliers to snap them off.

5

Smooth your curved edges using a glass router. This machine uses a spinning wheel with fine diamond chips as a grinder. Turn on the router and press your curve firmly against the grinder to smooth out your curve, then sand as normal.

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Community Q&A

Would a glass cutter cut mother-of-pearl tiles?

Answered by
wikiHow Contributor

You can cut any tiles you want with a glass-cutter. Just see it as a piece of glass, and when you've carried out the cut, place the handle of the glass-cutter exactly under the cut and press down firmly on both sides. The tile will break easily.

Is cutting a mirror the same as glass, and why is using a lighter a good way to tell how old a mirror is?

Answered by
wikiHow Contributor

Yes, a mirror is just a piece of glass, but cutting it requires a first step. A mirror is reflective because of the silver color coating on one side. This requires you to first cut the coating with a razor blade exactly on the line where your glass cut is going to be. If you don't do this first, the coating will peel at your cut and ruin your mirror.

I thought after you score the glass you are supposed to tap under the scoreline with a small tap to break it?

Answered by
wikiHow Contributor

That's not entirely "wrong." People tend to do what works best for them. If I am cutting a shape and don't need both pieces of cut glass, i.e; off cut may be discarded, I often place a dowel under the scored glass, slightly more to one side of the score line (the side I wish to keep) and I tap the off cut side to break it off.

It is better to give it a little tap under the score, but not too hard?

Answered by
wikiHow Contributor

A little tap is not always necessary. For 2 mm glass, just grasp the off-cut and bend it downwards. It should break cleanly and easily. However, 2 mm glass is only available up to a maximum width of 60 centimetres (and a normal length of 160 centimetres). If you're cutting glass thicker than that, then a light tap at the beginning of the cut will reliably start the run and the cut-off will peel off cleanly. You will also be able to see how the tap causes the cut to penetrate the thickness of the glass, and that's what you want to achieve. If it doesn't do that, then tap it again, but this time slightly harder.
MsG

How do I round the corners on cut glass?

Answered by
wikiHow Contributor

I use a knife sharpening stone. Just rub it on any sharp edge or corner. It's quick and it works well.

Am I supposed to cut the backside of the mirror with the razor blade/glass cutter?

Answered by
wikiHow Contributor

Normally, yes. The only exception is for "front surface mirrors" and they are not common items.

What do I use to cut glass?

Answered by
wikiHow Contributor

The tool can be bought at a home improvement store. It is called a glass cutter and has a small diamond impregnated wheel at the end.

What type of glass cutter tip is good for cutting glass?

Answered by
wikiHow Contributor

Carbide, diamond, and platinum are good - carbide being the most cost-effective.

Would it be okay to score the mirror with the glass cutter on the coated side only instead of the razor method?

Answered by
wikiHow Contributor

No, a glass cutter is not a knife. You should use a razor blade so the silver film on the back side of the mirror will be as clean as the glass cut. Remember, you will be looking through the glass side when you cut the glass so you can see the cut on the film. You cannot cut the mirror on the film side with the glass cutter as it will not score the glass; you will ruin the mirror every time.

Video

Tips

Practice on scrap glass until you get the technique down before trying the real thing.

Cut mirrored glass on the reflective side, not on the painted side. You will not be able to score the glass if you run your cutter over the painted back of the mirror. The technique for cutting mirror is otherwise exactly the same as cutting regular glass.

Reader Success Stories

TH

Tory Hart

Sep 11, 2016

"Thanks for the excellent guide. I really liked the small concise video clips for each step. I was replacing glass panes in an old 18th century cellar and the frames were uneven, so the glass that I had ordered needed to be trimmed. I had bought a glass cutter, but didn't have much of a clue beyond that point!"..." more

DV

Dawn Vollbrecht

Oct 17, 2016

"I have never cut glass before, but feel much better about trying it now. Showing the different ways to break the glass for a straight cut or a curve was interesting. The tips on not to proceed if the glass doesn't break. Also, practice was good."..." more

FM

Fiona McAlevey

Apr 6, 2017

"This was a great set of instructions. I'm a complete beginner to glass cutting, so really appreciated the whole task being broken down into manageable steps. The graphics were excellent additions which also helped my learning. Thanks!"..." more

DS

D. Shah

Oct 27, 2016

"I just bought a mirror glass, cut to size. Watched the guy cut it, clean it. Very clean work. I was inspired. This article, particularly the Q&A regarding safety tips, is very valuable. "..." more

JH

James L. Harris

Nov 9, 2017

"Wiping the glass was helpful, just thinking new glass is clean to cut isn't enough. Sanding the edge will also improve my skills. Very good information, thank you."..." more

RP

Robert Pearce

Nov 11, 2017

"Honest, straightforward article. Simplifies the mystery of cutting glass. Similar to the "score-and-snap" technique of cutting the good old ceramic tiles."..." more

KK

K. K.

Nov 19, 2017

"Very straightforward explanation. I needed to cut the edge from a small pane of glass for a clock face. Description and animated pictures were great. "..." more

Rated this article:

SJ

Steve Jordan

Oct 14, 2016

"Being able to cut your own glass is a fun, money-saving idea. The trick with the dowel is an excellent pointer; thank you!"..." more

DM

Denise McGuirk

Oct 11, 2016

"Great video instructions, very clear and easy-to-follow information. Covered all the pitfalls."